function get(url, fn){	
	//建立ajax对象
	var xhr;
	if(window.XMLHttpRequest){
		xhr = new XMLHttpRequest();
	}else{
		xhr = new ActiveXObject("Msxml2.XMLHTTP");
	}
	//建立连接
	xhr.open("GET", url, true);
	//发送请求
	xhr.send();
	//接收响应
	xhr.onreadystatechange = function(){
		if(	xhr.readyState == 4 && xhr.status == 200 ){
			if( fn ){
				fn(xhr.responseText);//回调函数
			}
		}
	}	
}

function post(url, arg, fn){	
	//建立ajax对象
	var xhr;
	if(window.XMLHttpRequest){
		xhr = new XMLHttpRequest();
	}else{
		xhr = new ActiveXObject("Msxml2.XMLHTTP");
	}
	//建立连接
	xhr.open("POST", url, true);
	//发送请求
	xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
	xhr.send(arg);
	//接收响应
	xhr.onreadystatechange = function(){
		if(	xhr.readyState == 4 && xhr.status == 200 ){
			if( fn ){
				fn(xhr.responseText);//回调函数
			}
		}
	}	
}